In this paper

the chopping current characteristic of vacuum switchgear is studied numerically when it interrupts the current with harmonic components. It is found that with the influence of harmonic

either the changing rate of current-zero may be decreased under some conditions

resulting in higher chopping current level

hence hazardous overvoltage

or the changing rate of current-zero may be increased resulting in lower chopping current level which makes the vacuum switchgear application safe.